On 8/25/20 9:01 PM, Josef wrote: >> In order for the patch to be able to move ahead, we'd need to be able >> to control this behavior. Right now we rely on the file being there if >> we need to repoll, see: >> >> commit a6ba632d2c249a4390289727c07b8b55eb02a41d >> Author: Jens Axboe <axboe@xxxxxxxxx> >> Date: Fri Apr 3 11:10:14 2020 -0600 >> >> io_uring: retry poll if we got woken with non-matching mask >> >> If this never happened, we would not need the file at all and we could >> make it the default behavior. But don't think that's solvable. >> >>> is there no other way around to close the file descriptor? Even if I >>> remove the poll, it doesn't work >> >> If you remove the poll it should definitely work, as nobody is holding a >> reference to it as you have nothing else in flight. Can you clarify what >> you mean here? >> >> I don't think there's another way, outside of having a poll (io_uring >> or poll(2), doesn't matter, the behavior is the same) being triggered in >> error. That doesn't happen, as mentioned if you do epoll/poll on a file >> and you close it, it won't trigger an event. >> >>> btw if understood correctly poll remove operation refers to all file >>> descriptors which arming a poll in the ring buffer right? >>> Is there a way to cancel a specific file descriptor poll? >> >> You can cancel specific requests by identifying them with their >> ->user_data. You can cancel a poll either with POLL_REMOVE or >> ASYNC_CANCEL, either one will find it. So as long as you have that, and >> it's unique, it'll only cancel that one specific request. > > thanks it works, my bad, I was not aware that user_data is associated > with the poll request user_data...just need to remove my server socket > poll which binds to an address so I think this patch is not really > necessary > > btw IORING_FEAT_FAST_POLL feature which arming poll for read events, > how does it work when the file descriptor(not readable yet) wants to > read(non blocking) something and I close(2) the file descriptor? I'm > guessing io_uring doesn't hold any reference to it anymore right? Most file types will *not* notify you through poll if they get closed, so it'll just sit there until canceled. This is the same with poll(2) or epoll(2). io_uring will continue to hold a reference to the file, it does that over request completion for any request that uses a file. -- Jens Axboe
